Biogeochemical characteristics of phosphorus play a significant role in eutrophication processes. Phosphorus may accumulate in lake sediments during heavy loading periods and release from sediments into the overlying water after the external loading is reduced. The released phosphorus sustains the eutrophication processes and cycles between overlying water and sediments through algal growth, organic deposition, decomposition, and release. Therefore, phosphorus is generally recognized as the limiting factor in the process of eutrophication. Restoration efforts to control phosphorus from WWTP into rivers are considered to be important strategies for decreasing cyanobacterial risks in the environment.
To reduce levels of phosphate, some design principles and various mechanisms are recently adopted to produce low effluent TP concentrations in urban WWTP. The effluent TP concentration is an index of water qualities in the urban WWTP. However, using conventional technologies, it is difficult to timely estimate the effluent TP concentration under closed-loop control. The timely and/or online detection technology of effluent TP concentrations is a bottleneck for the control of the urban WWTP. Moreover, the real-time information of effluent TP concentrations can enhance the quality monitoring level and alleviate the current situation of wastewater to strengthen the whole management of WWTP. Therefore, the timely detection of effluent TP concentration owns both great economic benefit and environmental benefit.
Methods for monitoring the effluent TP concentration may include spectrophotometry method, gas chromatography method, a liquid chromatography method, electrode method, and mechanism model. However, the spectrophotometry method, gas chromatography method, liquid chromatography method and electrode method rely upon previously collected data analysis of primary variables. Some of the variables, such as gas chromatography method, require more than 30 minutes to obtain. This makes these approaches inadequate for real-time and/or online monitoring. The mechanism model studies the phosphorus dynamics to obtain the effluent TP concentration online based on the biogeochemical characteristics of phosphorus. However, significant errors may be incurred in the measurement of effluent TP concentrations. Moreover, because of the different conditions of every urban WWTP, a common model is difficult to be determined. Thus, technologies for timely monitoring effluent TP concentrations are not well developed.